Technical Field
The disclosure relates to a software defined network (SDN), a mobility management method and a controller thereof.
Related Art
Started From 2012, software defined network (SDN) becomes a hot topic. A difference between the SDN and a conventional network is that a controller is added in the SDN. The controller manages a topology and routing paths of the whole SDN. The controller can dynamically adjust the routing paths according to a real-time status of the network, so as to reduce a network congestion to improve a network performance. The controller and the dynamic routing are characteristics of the SDN.
However, the current SDN is only adapted to cable networks, although a standard-setting organization (the open networking foundation (ONF)) of the SDN has taken wireless networks into consideration, design of the SDN is still not adapted to applications of wireless mobile networks.
If a wireless mobile network system adopts the current design of the SDN, it is assumed that a radio access network (RAN) of the wireless mobile network system is a Wi-Fi network, when a user equipment (UE) is handed over from one access point to another access point, the controller does not immediately adjust flow entries of related switches and access points. After the UE sends the first packet after the handover, the access point attached by the UE sends a standard packet_in message to the controller only when determining that there is no flow entry related to the UE after comparison. Now, the controller sets the flow entries of the related switches and the access points. Before adjustment of the flow entries is completed, the access points and the switches in the SDN cannot route packets for the UE. This period of time that the packets cannot be routed is referred to as a handover delay.